Many researchers have the habit of using three dimensions to display a two dimensional graph. There are worse examples than the one above, but it is both unnecessary and counter productive. First there is ambiguity as to where the tops of the bar lie. Second, there is no information contained in the third dimension. Remember, don't add any complexity that doesn't support the message you hope to convey.
This slide graph has lots of other problems. The fonts are too small and too dim. The vertical axis label needs to be written horizontally. The audience will waste a lot of time trying to read the axis rather than listening to the speaker. There is not so much information on this graph that it can't be made smaller to accommodate a horizontal label. The legend is also bad. I would simply print the words in red and gray colors (with bigger letters) and put them in the main part of the graph, no need for the little boxes. The title can be used to help guide the audience toward the main message, perhaps, "There Has Been a Steady Increase in Clinical Research Services."